Formation of Glyoxylic Acid in Interstellar Ices: A Key Entry Point for Prebiotic Chemistry

Abstract

With nearly 200 molecules detected in interstellar and circumstellar environments,t he identification of the biologically relevant a-keto carboxylic acid, glyoxylic acid (HCOCOOH), is still elusive.H erein, the formation of glyoxylic acid via cosmic-ray driven, non-equilibrium chemistry in polar interstellar ices of carbon monoxide (CO) and water (H 2 O) at 5K via barrierless recombination of formyl (HCO) and hydroxycarbonyl radicals (HOCO) is reported. In temperature-programmed desorption experiments,the subliming neutral molecules were selectively photoionized and identified based on the ionization energy and distinct massto-charge ratios in combination with isotopically labeled experiments exploiting reflectron time-of-flight mass spectrometry.These studies unravel akey reaction path to glyoxylic acid, an organic molecule formed in interstellar ices before subliming in star-forming regions like SgrB2(N), thus providing ac ritical entry point to prebiotic organic synthesis.

Interstellar Formation of Biorelevant Pyruvic Acid (CH3COCOOH)

“…[20][21][22] In general, hydroxycarbenes undergo barrierless carbonyl ene reactions with carbonyl compounds in the gas phase, yielding biorelevant molecules, including the carbohydrates glycolaldehyde and glyceraldehyde. 23 Eckhardt et al 24 and Turner et al 25,26 recently demonstrated the formation of glyoxylic acid (HC(O)COOH) and even (di)phosphates (PO 4 3À /P 2 O 7 4À ) in ices modeling interstellar conditions, providing compelling evidence that essential biorelevant molecules, together with their precursors, might form in deep space. At least a fraction of these abiotically synthesized compounds might be incorporated into meteoritic parent bodies and could have survived successive meteorite or comet impact on the Earth, thus reinforcing the theory of an exogenous source of key prebiotic molecules on the Earth.…”

Effects of Geochemical and Environmental Parameters on Abiotic Organic Chemistry Driven by Iron Hydroxide Minerals

“…For understanding how the emergence of metabolism could have occurred in a geological environment, much work focuses on studying reactions of organic molecules that are both important to modern biology and also are likely to have been present at life's origin. Pyruvate and glyoxylate are two carboxylic acid compounds that are of particular prebiotic interest: They are central to modern biochemistry, can be synthetized abiotically (Cody et al., 2000; Echkardt et al., 2019; Eggins et al., 1988; Marín‐Yaseli et al., 2016; Mohammed et al., 2017; Varma et al., 2018), and can lead into a variety of important reaction pathways for origin of life including reactions that resemble ancient proto‐metabolic cycles (Muchowska et al., 2017, 2019). In previous studies, pyruvate and/or glyoxylate have been shown to react with redox‐active iron minerals and/or dissolved Fe 2+ and various nitrogen sources to form amino acids, alpha‐hydroxy acids (αHA's), thiols, and other citric acid cycle intermediates (Barge et al., 2019; Huber & Wächtershäuser, 2003; Muchowska et al., 2017, 2019; Novikov & Copley, 2013).…”